Transistor Circuits

Let Us Learn About Transistor Circuits

The circuits we have encountered so far are passive and dissipate power. Even a transformer that is capable of giving a voltage gain to a circuit is not an active element. Active elements in a circuit increase the power by controlling or modulating the flow of energy or power from an additional power supply into the circuit.

Transistors are active circuit elements and are typically made from silicon or germanium and come in two types. The bipolar transistor controls the current by varying the number of charge carriers. The field effect transistor (FET) varies the current by varying the shape of the conducting volume.

Before starting we will define some notation. The voltages that are with respect to ground are indicated by a single subscript. Voltages with repeated letters are power supply voltages. And voltages between two terminals are indicated by a double subscript.

Important of Transistor.

Switching

1. Transistors make excellent electronic switches. They can turn currents on and off billions of times per second. Digital computers use transistors as a basic mechanism for storing and moving data.

Amplification

2. Properly set up, transistors can serve as amplifiers. The vast majority of audio and other signal amplifiers are transistorized.

Miniaturization

3. Depending on the application, transistors can be made very small. The transistor size in 2009 is billionths of a meter. Masses of tiny transistors packed on silicon chips let us create pocket-sized cell phones and Mp3 players.

Efficiency

4. Transistors can be designed to use very little power. Millions of them in a watch or calculator can run for years on a small battery.

Rugged

5. Transistorized equipment is used in military, space and industrial applications. They can withstand extremes of shock and vibration.